Cheap 10s Lithium BMS

[DudeeBalls]

I found the following BMS on ebay and wanted to know what you all think of it. I'm thinking of using the BMS to balance charge my recycled laptop 18650 10s 40ah battery pack in conjunction with some kind of bulk lithium charger while on the go and away from home (got an iCharger 1010B+ for home). I'll probably bypass the BMS for discharging (draining the pack while riding) cause I figure I can't count on it's 30a rating at that price and that it'll serve more as charge protection/balancer for my potentially easily unbalanced pack due to the use of so many batteries from different sources with potentially different capacities and/or internal resistances. I'm almost out of money with all the recent investments in my electric bike project so if anyone could recommend a 10s bulk lithium charger to use with this BMS that won't cost me as much as the charger or more for shipping and does at least 5a (so it won't take more than 10 hours to charge my 40ah pack) it would be much appreciated. I've heard stuff from meanwell mentioned but I don't know much about that and there's a new 10s 36v6a one from BMSBattery called the S240 but it cost $73.39 after shipping ($30 before) and ebay only has one listed that's aluminum 10s and 5a but it cost around $83 after shipping. Both of which would be no biggy if I hadn't already broken the bank on the iCharger and the special balance cables for it (which cost a lot in and of themselves).

In case anyone is wondering why I made a 10s24p battery (240-18650's) it's not cause I intend on going to the moon and back without refueling it's because I bought them like that from some guy on craigslist who gave up on his own ebike project after making it. I'm gonna break it up (cut the tabs between each 24-pack and untape/uncardboard them from one another) into 10 24p groups so I can put a balance lead on each set then maybe I'll put cardboard and tape around each pack and connect them in series with wires/connectors so if one goes seriously wrong it won't damage the others as much, they can be traded out easier etc. I don't trust just charging it as is without balance leads cause I don't really know much about what testing the guy did prior to connecting it all (it measures 35 point something volts as it came). For some odd reason one of the packs of 24 has rust all over the top of it including on the solder tabs as if battery acid poured all over it after it was all soldered together but I haven't found the source yet so perhaps some had burst and he removed them. I had someone pick the cells up for me out of town and the guy who sold them was Chinese I think and spoke very poor English so I wasn't able to understand any of his answers but for $100 for what looks to be around 405 18650's I think it's a pretty sweet deal. He even threw in a few sets of flatish small cellphone looking batteries strung/taped together that I think may have been from some kind of old/oddschool laptops and some of the laptop packs aren't even hacked open yet but I included them in my total estimate.

Features:

size : 53*63MM
Over charge voltage test: VCU 4.25V ±0.05V (4.20-4.35V // each 0.05V per step)
Over charge voltage resume: VCD 4.10-4.00V
Over discharge voltage test: VDD2.50V ±0.1V (2.5-3.0V // each 0.05V per step)
Over discharge voltage resume: VDU 2.80V ±0.V1

Operating current: ≤300UA
Short circuit protection: 40A±3A
Short circuit protection duration: 500MS
Temperature protection: 55 / 65 / 75 degree
Typical output current: 30A

Max. output current: 45A
Balance voltage for single cell:4.19V ±0.02V

Balance current for single cell：≤ 55MA

Charging current：≤10A
Dim. 53 x 63mm (L x W)

 

[dnmun]

the rust is created by the hydroflouric acid formed when the electrolyte inside the cell is leaked out to the outside of the cell.

there are no pictures of the battery here so nothing to help you with.

 

[Ykick]

I would only expect 15A continuous (if lucky) from that BMS so bypass discharge will likely be in your future. Cheap price though.

I’ve never done this yet but I’ve often considered reconfiguring discharge P- side of a low power BMS to switch a warning light/buzzer circuit instead of interrupting system power? I think it could be done for cell level LV warnings?

 

[DudeeBalls]

Here's the pics. Concerning Ykick's comment about hooking up some kinda alarm triggered by the BMS why not just hook up an lvc alarm as well as a BMS by connecting two sets of balance leads in parallel to each other (one for the lvc alarm) or if not using it for discharge and only for charge then just plug the balance leads into the lvc alarm instead of the BMS while riding (what I might do). The Cell-Log 8M seems pretty cool so I ordered it but since I have 10s and it only does 8s I'll probably be getting a cheap little generic lvc alarm for the remaining 2 (probably one with a basic cycling LED readout so I can know the voltage of all cells). On a side note I've been thinking it might be pretty cool to get a MKS Propo 3 in 1 Balancer at some point down the line to beable to do quick balance adjustments on the road if needed.



(Click on the pics to see them full size)

 

[Grizzl-E]

I actually bought one of these Bms. The build quality looks ok but it's still sitting on my desk so no comment on reliability. It is very small.

As for those batteries. Omg. That looks like the most dangerous pack I've ever seen and I wouldn't trust a single cell. Looks like they tried to solder with a low wattage iron and probably dumped way too much heat into those cells.

If you have a lot of time on your hands and want to use them however, take every one apart and properly test them. There are scades of threads on methods so I won't go into that. But I wouldn't trust the guy who made that pack to have tested for bad cells in any way.

I'm not against lap cell builds for low wattage builds but they take a lot of time to do right. And dude keep that thing in a steel garbage can in case it goes boom. Good luck with your build.

 

[DudeeBalls]

A lot of them seem ok and some of it seems to be spot welded (though oddly some soldered also) it's just that 24-cell pack that has all that acid damage that has me worried. In any case at the very least I plan on separating them into 10 24-cell bricks and covering them each in cardboard plastic and duck tape. I might dis-join that sketchy looking rusty set and see if I can locate the leak and if any of those can be rescued. It would also be nice to separate them in half so I can have two 120-cell pack instead of one 240-cell pack cause it's way to heavy and pretty big too. My balance cables and 8 cell battery monitor came in today so I'm all ready to get started though I would like a hotter soldering gun. Should I get a dremel to sand/clean the cells before soldering to them (especially the acidy ones if any of them are fully intact). I bought 50x 1/4" x 2" x 0.005" solder tabs off of amazon but in case they're not enough I got a few feet of a single conductor 10awg copper wire and I've also been toying with the idea of flattening it to make my own battery "tabbing" strips.

 

[Grizzl-E]

If you want to be safe first thing you should do is make a jig to balance charge 10 cells at a time with that nice charger. I make my jigs with my 3d printer but it doesn't have to be fancy.

Take the individual cells out of the pack, charge them to 4.2v at 1/2c or less. Any that get hot while charging throw out. Leave them overnight and check the voltage. Anything that's dropped under 4v don't use. You only want the best ones.

I know this is not what you want to hear but lico lap cells are potentially very dangerous if they have developed internal shunts or high resistance. Most experienced guys won't use them. But don't take my word for it. There are tons of threads on reusing lap cells and the precautions that need to be taken.

Be safe. You have enough cells there that you can have an awesome pack that will last a long time if it's built right.

 

[999zip999]

The leaking stuff could be electrolyte leaking from the cells from to much heat from a soldering iron. A low wattage or to small a soldering iron takes to long to heat up the cell. This causes the seal on top of the cell to go pop and leak. Maybe.

 

[dnmun]

no, they vented because they were overdischarged and then recharged. no storage capacity left and were charged without a BMS to protect them so they vented and that is why the HF has corroded everything. all just a waste of time. this guy is gonna solder 10AWG wire to it so there is no way it is not gonna be damaged. no matter what type of soldering iron.

 

[999zip999]

Agreed. Looks very dangerous.

 

[DAND214]

I would like a hotter soldering gun.

YOU DON'T WANT A GUN!
Iron not a gun. there is not enough mass in a tip on a gun to do the job.

Dan

 

[DudeeBalls]

Sorry for the wrong term I meant iron not gun. I'm self taught so I'm a bit bad with terminology.

 

[dnmun]

but the cells have all been ruined by the guy who built it up and sold it to you. they were over discharged so they are mostly useless now and that is why they have the HF corroding them because they were recharged after that so some of the cells were overcharged and popped the vents.

grissly laid out what you have to do to find any of these that may hold charge and have relatively low internal resistance. you would be better off starting from scratch with new cans imo.

find a better BMS that doesn't use the opto transistors, and build a 15-16S pack instead.

 

[DudeeBalls]

Only 24 pack of cells out of the 240 cells are like that so at the very least I'll try to recover the others or at least see if they're recoverable. I guess I'll break all the packs up into individual cells, clean them up, check their capacity and maybe even internal resistance with my new iCharger 1010b+ and build it up from there. They obviously can hold a charge though since they've been at 35v since I bought them over a month ago. I bet if I make a 10s 120-cell pack and make each of the 10 bricks narrow I could probably fit them all into my large ibera frame bag that I just bought online mistakenly thinking it was wider than it is.

One of my biggest inspirations for this project is Rinoa Super-Genius's videos on youtube but although I got most of what he used I still haven't found a good/cheap source for those magnets he uses to series charge his 18650's without a bunch of battery holders (don't even know what size they are). I did buy 6 2s 18650 holders off amazon but I'd still like to try the magnet method. It seemed like such a simple yet cool idea.

On a side note what do you all think about these 12V 30A Switches I found on amazon? I already bought and intend to use a Master Battery Cut Off for my 36v presumably 20a used Crystalyte front hub kit but it would still be cool if I found a regular switch that can handle an ebike's power cause the cut off is very bulky. I saw a video on youtube once in which some guy used a big red led rocker in a hole he made in a trunk bag with some lipo rc packs inside but I've never been able to find one like that with a high enough amp/volt rating. Perhaps he was pushing the limits and had just been lucky so far.

 

[Grizzl-E]

Some good threads on the subject of lappy builds:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=46756

http://endless-sphere.com/forums/viewtopic.php?f=3&t=26383

As for switches does your controller have an on switch input? Those switches may be fine but a solid state solution would be better. Or just use these and unplug your batteries:

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=61690&aff=900621

I would suggest these connectors for all ebike batteries to keep your connectors good. Best if you pick a system and stick with it so you can swap out batteries and controllers and always have the same connectors.

 

[DudeeBalls]

My stupid controller doesn't have a power switch input it must be one of Crystalyte's earliest versions of their 408 kit cause I've found pics online of a Crystalyte 408 kit that had a switch on the controller. for now my preffered connector is the Anderson 45amp but I can't afford the anderson crimper and have had some bad luck with crimps on their difficult 45amp open design so I bought 4 m/f pairs of XT60's but I do like how small, interchangeable and easy to connect/disconnect Anderson's are (not to mention the Crystalyte controller came with Anderson).

 

[Grizzl-E]

In that case I would try the switch since you have it. You may want to wire it up in a loop that can go between your main connections. That way if the switch contacts go poof you can just unplug it and plug the battery directly into the controller.

If you haven't vaporized anything then your not really a diy ebike builder lol. You have to earn those dead spots on your retinas!

 

[dnmun]

the switch in the C'lyte controller is in the circuit current on the controller and it is not in the power circuit to the output mosfets so it is a low current switch.

 

[DudeeBalls]

I don't actually have those 12v 30a switches. The one I bought was the master battery cut off switch which is a massive old hunk of switch with a 300a capacity. I don't really understand dmnum's comment about the current circuit. I have some pics of my controller's circuit board on my Crystalyte post but as you can see the only unoccupied connector on the pcb is the ebrake (which I would like to get an unrelated cheap ebrake I found for and take a connector off a computer fan for it but I don't know how I'd figure out the pin out of the ebrake or the ebrake's connector on the pcb). I just had a friend open one of the 6-cell laptop packs that was still sealed today and we tested it and it came to a-3.48 b-2.50 c-3.34. Kinda strange since it had a mini BMS managing it's balance. The the pair on the end was warm so I figure he probably shorted it with the screwdriver he was using to pry it open but just for a second or so.

I really like the BMS with the digital lcd readout below but I bet it's expensive as hell that's if I could find it.

 

[Grizzl-E]

If those lap packs are used then expect to find 1-2 bad cells per pack.

I haven't found a cheap battery gauge that has an accurate capacity display. You'll see a lot of guys including myself using these:
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=10080&aff=900621

Cheap and accurate for the price. If you want better you may want to save for a cycle analyst. They are totally worth the 120 U.S. (Not sure where your located)

 

[dnmun]

it just seems so backwards to waste hundreds and hundreds of dollars on these balance chargers and power supplies and fancy BMS and now another cell monitor when just buying a decent battery initially would have cost the same amount.

 

[Grizzl-E]

it just seems so backwards to waste hundreds and hundreds of dollars on these balance chargers and power supplies and fancy BMS and now another cell monitor when just buying a decent battery initially would have cost the same amount.

I don't think so. If 70% of his 400 lappy cells are good and he gets 2ah out of each those, which is not unrealistic, he will have 2kw of batteries. Pretty good value imho. Plus good chargers etc are an investment.

That being said I've built large 18650 packs and have a healthy respect for the amount of labor that goes into it. Especially if your trying to properly test and match used lap batteries.

All of this cost is insignificant to how much you learn when you take on any project like this yourself. I'm a real believer in buying the tools and making it yourself after researching a subject to death. I encounter professional engineers all the time that have to bear the burden of not having hands on experience. It sucks for them and the people who have to make their designs work.

Sorry for the rant. My day job is %50 tech support on some pretty complex equipment. I wish more people were willing to expand their knowledge base through their personal interests and projects.

And believe me, it is always cheaper for me to pay for a finished product these days. But if I had though like that 15 years ago I wouldn't make what I do now.

 

[999zip999]

Hey dudeeballs where do you live ?

 

[DudeeBalls]

I do have one of those GT watt meters with the same specs. Just thought that detailed BMS was cool. I'm in So Cal. I understand both points I do feel a little overwhelmed and am wondering if I should have just bought an ebay LifePo4 36v 15ah for around $300 from china but I also am kinda excited by the possibilities and of coarse intimidated by the work (not to mention a little scared of the combustibility).

 

[DudeeBalls]

The guy in this youtube also uses an interesting little lcd BMS meter but doesn't look as detailed as the other. I hope I can find a cheap semi bulk source for those 18650 spacers/holders that I've seen used here and there on some youtube's and elsewhere cause they seem like they'd make changing out a bad cell a 100 times easier than using hot glue.